I'm interested in building up math intuition too. I'm engaging with math very slowly and just as a hobby, but part of what got me interested was encountering resources that are unreasonably effective at building intuition.
A common theme I have noticed is whatever it is, getting a geometric understanding of it aids intuition significantly. Others have mentioned the 3Blue1Brown videos. They are an excellent example of this.
These HN threads always bear out great resources and I've made note of (and acquired) a few of these, so I'll list them here.
Burn Maths Class - https://www.goodreads.com/book/show/26195956-burn-math-class
Book of Proof - https://www.people.vcu.edu/~rhammack/BookOfProof/
The Topology Of Numbers (number theory)- http://pi.math.cornell.edu/~hatcher/TN/TNpage.html
The Evolution of Trust (game theory) - https://ncase.me/trust/
Visual Information Theory - https://colah.github.io/posts/2015-09-Visual-Information/
Information Theory For Smarties - http://tuvalu.santafe.edu/~simon/it.pdf
Abstract Algebra - https://www.youtube.com/playlist?list=PLi01XoE8jYoi3SgnnGorR...
Algebra Cheatsheet - https://argumatronic.com/posts/2019-06-21-algebra-cheatsheet...
Control Theory Basics - https://www.youtube.com/user/ControlLectures/playlists